Bearings, which are sealed off are today used in many applications. At bearings having small or no angular misalignments at all, the seal will function in an appropriate manner. A large number of different solutions are available on the market for this type of bearings. The size of the bearing is of less importance in this regard.
Regarding spherical bearings and other self-aligning bearings, there are however problems as these bearings are made for handling large angular misaligments. For using seals in those types of bearings it is necessary to compromise. Such compromises can be to make a sphered surface on the inner ring against which the seal engages, to reduce the contact angle, which has influence on the load carrying and/or to restrict the ability of the bearing to make angular motions. A typical maximum misalignment for a sealed off spherical roller bearing is 0.5°.
It is of course not a good solution to provide a self-aligning bearing with built in seals, which highly reduce the ability of the bearing to make angular adjustments.